Audio amplifier



FIG. 1 is a top, front and right side perspective view of an audio amplifier showing my new design;

FIG. 2 is a top, front and right perspective view thereof, shown with the cassette cover in the closed position;

FIG. 3 is a top plan view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a left side elevational view thereof;

FIG. 7 is a rear elevational view thereof; and

FIG. 8 is a bottom plan view thereof. 

The ornamental design for an audio amplifier, as shown and described. 